* src/newusers.c: Fix the check for GID/UID validity.

	* src/newusers.c: Fix the check for GID/UID validity.
	* src/newusers.c: Comment why we use both getgrgid() and
	gr_locate_gid().
	* src/newusers.c: Cast the parsed GID/UID to a gid_t/uid_t.
	* src/newusers.c: Cast the number of days to a long integer.
	* src/newusers.c: Use SHADOW_SP_FLAG_UNSET for the initial
	value of spent.sp_flag.
	* src/newusers.c: The size argument of fgets is an int, not a
	size_t.